In this tutorial I will be building a dynamic patch antenna. I will discuss the basic principals governing the patch and how it works as well as how to adjust and tune it to meet your specific needs. This is different from RC Cams Goof Proof Patch, which is also an excellent antenna.
I am constructing this out of 26 gauge galvanized steel, but any conductive metal will work well. Thin galvanized steel (22-30 AWG) works well and can be found for $5-6 at most hardware stores. I bought mine at Lowes in a 12X24 sheet for $6.

For the bolts and spacers I am using ¼-20 nylon bolts and 1/2  spacers. You can use any non conductive bolt or even wooden blocks as spacers.

I will update this thread periodically with more theory and principals later. I will also see if I can model the radiation patterns.

Calculations: Calculating your length and width

The first thing you need to do is calculate your ½ wavelength for your frequency. The formula is:

½ Wave in inches = 5124/f in MHz
Or for you metric folks:
½ Wavelength in mm = 130150/f in MHz

This measurement will be the length of your active element. For my 1280 MHz patch, my element is 4-1/16” long.
The length of you element is you ½ wavelength measurement. Now we need to get the width. As the width of the antenna increases, it lowers the impedance of the antenna. However this also changes the radiation pattern. For the patch your width can be anywhere from 3/2 to 4/3 of your length. 3/2 will yield a 50 ohm impedance. 4/3 will yield 75 ohm impedance in theory, but in actuality, it still hits close to 50 ohms. In fact, you can almost make it square. The width affects the radiation pattern more than anything.

So for 50 ohms:
Width in inches = 7686/F in MHz
Or
Width in mm = 195227/f in MHz

For 75 Ohms:
Width in inches = 6832/f in MHz
OR
Width in mm = 173535/f in MHz

Which do you use? It’s up to you. You can pick any value in between those two widths and the antenna will work well. A wider panel will give you a wider beam width but reduce gain slightly. A 50 ohm antenna will have a beam of ~ 90 degrees and a 75 ohm will have a beam of ~75 degrees. Both will work well with your RX. For my 1280MHz I made mine 6 - 1/8” which will give me a wide beam width and an impedance of about 50 ohms.

Assembly: Drilling your holes

Assembly drilling your holes:

Now that you have cut out your elements, now it is time to build your antenna. First you need to drill out a small hole in the active element where you plan to connect your coaxial line. This should be dead center width wise and the same distance from the edge as your height. So for my 1280 MHz patch, this is located at 3-1/16 from either side and ½ from the bottom.

Now you need to drill the holes for your nylon bolts. Where you place them is entirely up to you. I put mine 1 from the corners. Place your active element in the center of your ground panel and tape them together and drill them as one plate. This will ensure proper alignment. Once done, mark your active element hole and drill that such that you can pass the center element of your coaxial line through it.

Assembly: Constructing the antenna

Place your spacers (you can use spacers, washers, or even wood) between your panels, pass your bolts through and secure them. Now make a small solder bead around the coaxial line holes.

Strip your coaxial line and flare out the shield. Strip the insulation off of the top of the center element. Now pass your cable through the backside of the ground panel. Solder the shield to the ground panel and the center element to the active panel.

No go out and try it! The best results will be achieved when the edge of your active element is about ½ wavelength off of the ground. Experiment with this height to achieve best results.

Still learning here. What is the purpose of a patch antenna? I regret I never took the time to learn much about electronics. At age 50+ and working to learn about FPV, I may be at a bit of a disadvantage.

The best results will be achieved when the edge of your active element is about ½ wavelength off of the ground.

I think there was another thread which someone posted this suggestion, quoting you as the source. Is it that the ground acts like another reflector? is this only with patch types? Will it still be a general improvement if the terrain is such that the LOS might be slightly less at the ground instead on on a tripod?